I observed that a lot of people are having difficulties finding out the websites for various embassies where then intend to apply for th their visa; and often times we see people asking for the link of this and that embassy.
So, here are the links to both online application websites and for printable application form:

 For the UK visa, Click here:
http://www.visa4uk.fco.gov.uk/Welcome.htm

These are for IRELAND:
http://www.inis.gov.ie/en/INIS/Pages/Information_on_completing_your_online_application
http://www.dfa.ie/home/index.aspx?id=74989

For those applying for a visa to CANADA:
http://www.cic.gc.ca/english/my_application/apply_online.asp

For the USA:
https://ceac.state.gov/genniv/

AUSTRALIA is here:
http://www.immi.gov.au/e_visa/

You can find a form for NEW ZEALAND application here:
http://www.immigration.govt.nz/migrant/general/formsandfees/formsandguides/

For SCHENGEN visa, note that for the reason that there are 25 Schengen signatory counties, the Schengen Visa Application link has numerous sub links which you will need to navigate to get to the country that you mainly intend to apply to.
Click here: http://www.schengenvisa.cc

Note: Not every embassy of the listed countries that supports the online application system, so it is important to have adobe installed in the computer from which you intend to print out the application

D LINKS ARE GOOD BUT BEFORE NOW, I HAVE CHECKED SOME OF THEM. CANADA YOU CAN APPLY ONLINE BUT NEW ZEALAND AND AUSTRALIA, NIGERIANS CAN'T APPLY ONLINE.

@Vicjustice, ARE WE NOW ACCEPTED TO APPLY ONLINE IN THOSE COUNTRIES

henrychubayo: D LINKS ARE GOOD BUT BEFORE NOW, I HAVE CHECKED SOME OF THEM. CANADA YOU CAN APPLY ONLINE BUT NEW ZEALAND AND AUSTRALIA, NIGERIANS CAN'T APPLY ONLINE.

@Vicjustice, ARE WE NOW ACCEPTED TO APPLY ONLINE IN THOSE COUNTRIES

Like I said, "not every embassy of the listed countries that supports the online application system, so it is important to have adobe installed in the computer from which you intend to print out the application"